Errors exist in required project(s) occurs when eclipse runs a Java file

The following problems may occur when eclipse runs Java:

first select Cancel to solve the problem:

1. The first type: It may be a java environment problem, that is, a problem with the JRE.
   
2. The second type:
   If the following problems occur after selecting Proceed to run:
   

It is an error in your own Java file:

• The reason for the error may be that the package is not specified in the code or the package is specified incorrectly
• Unhandled exception type Exception appears like the author: Unhandled exception type Exception

The calling method of the Connection object did not throw an exception, which resulted in an error being reported as Unhandled exception type Exception, which can be solved by doing a try-catch exception throw.